Haematoporphyrin derivative of uncertain specific composition (HpD) have been used in the treatment of tumors in man susceptible to necrosis by a porphyrin, having been found to locate in tumours (and other tissues) after injection into the bloodstream and to sensitise cells to light irradiation (transport in the blood is believed to be largely in association with the serum albumin). Irradiation, with a laser or other source, may be direct or indirect, for example using fibre optics. Irradiated cells (unless deeply pigmented) are rapidly killed to a depth depending on the light penetration. The mechanism of cell killing in phototherapy is believed to be largely by production of singlet oxygen. This is produced by transfer of energy from the light-excited porphyrin molecule to an oxygen molecule. Singlet oxygen is highly reactive. It is believed to oxidise cell membranes so that they are damaged and become incapable of exerting their function of controlling the cell's internal environment. This rapidly leads to cell death.
In addition to the use of HpD there is prior art in the literature of tumour-locating tetraphenyl porphyrins in Chemical Abstracts 90 12 (1979) 132517s where carboxyl and sulphonate (hydroxysulphonyl) substitutents are shown in phenyl rings, and in Chemical Abstracts 97 795 (1982) 182083n where unsymmetrical functionalised derivatives of tetraphenyl porphine are shown, which the "Health Sciences, Dentistry" article itself shows to be 5-hydroxyphenyl-10,15,20-tricarboxy phenyl porphyrins in the form of derivatives of N,N-bis(2-chloroethyl) phosphorodiamidic acid. More peripheral publications are U.S. Pat. No. 4,386,087, disclosing leukaemia treatment with sulphonated tetraphenyl porphyrins, and EP A-0 066 884, disclosing iron complexes of substituted tetra-amino porphyrins for use as oxygen absorbing and desorbing agents. Chemical Abstracts 100 358 (1984) 109155p shows similar oxygen carrying systems and U.S. Pat. No. 4,307,084 related ones using carboxyl substituted compounds.